A bar code symbology is a set of encoding algorithms, that essentially provides the grammar for the production of a bar code pattern. As in written languages, bar code symbologies have rules of grammar that dictate how the pattern of bars and spaces are formed for any particular coded data.
Among the most common bar code symbologies in the U.S. and Canada is the Universal Product Code (UPC-A). Referring now to the drawings wherein like numerals indicate like elements, there is shown in FIG. 1 a bar code symbol 10. The bar code symbol 10 comprises has a linear portion 12 and a human readable portion 14. The linear portion 12 comprises a pattern of bars 16 and spaces 18. The dimensions of the bars and spaces in the symbol are typically exact multiples of a unit bar. The unit bar is a narrow bar having a predetermined width for a bar code symbol at a given magnification.
FIG. 2 shows an example prior art bar code image that has the RSS-14 Limited bar code symbology. Such a bar code comprises a two-dimensional component 20 that is coupled to ends of the linear portion 12 of the bar code. Much more information can be encoded into an RSS-14 limited bar code image than a UPC-A bar code image, and therefore, no human readable portion is shown in the bar code image in FIG. 2.
Prescription drugs, other medications, and some medical devices employ a method that uses two bar coded labels to expedite record keeping. Known in the art as “double bar-coded labels,” two identical bar codes are printed on a single label. One of the bar codes appears in the main body of the label. The second bar code appears on a portion of the label intended to be removed by, typically by tearing through perforations. Whenever a product having a double bar coded label is administered to a patient, the removable portion of the label is torn from the product label and applied to the patient's record, for example, via a self-adhesive backing.
The prior art method of using double bar coded labels, however, carries the possibility of errors. For example, the two bar codes comprising the double bar coded label may be printed such that one bar code may not match the other. Moreover, one of the bar codes in the double bar coded label may be unreadable. In such case, the product may be scanned into hospital records but the label applied to the patient record is unreadable.
Additionally, printing two bar codes on a single label can be difficult and time-consuming. For example, a graphic designer who prepares artwork comprising double bar coded labels may mistakenly place two different bar code images in the artwork instead of two copies of the same bar code image. The information encoded in the bar code image is not human readable, and the information encoded in the bar code image may not be printed in human readable form. Moreover, the graphic designer must perform quality control to check his or her work for accuracy. To this end, and to prevent bar code production errors, bar coded labels must be verified with electronic verifiers to assure ability of each bar code to be printed and read. The verified results of each bar code are compared to each other to ensure the data match. The comparison is typically done manually, and therefore can also result in error.